21523959 has 12 divisors (see below), whose sum is σ = 31144152. Its totient is φ = 14324400.

The previous prime is 21523949. The next prime is 21523961. The reversal of 21523959 is 95932512.

It is a happy number.

It is not a de Polignac number, because 21523959 - 2⁵ = 21523927 is a prime.

It is a super-2 number, since 2×21523959² = 926561622067362, which contains 22 as substring.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523949) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4489 + ... + 7949.

It is an arithmetic number, because the mean of its divisors is an integer number (2595346).

Almost surely, 2^21523959 is an apocalyptic number.

21523959 is a deficient number, since it is larger than the sum of its proper divisors (9620193).

21523959 is a wasteful number, since it uses less digits than its factorization.

21523959 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4158 (or 4155 counting only the distinct ones).

The product of its digits is 24300, while the sum is 36.

The square root of 21523959 is about 4639.3920937985. The cubic root of 21523959 is about 278.1681392328.

The spelling of 21523959 in words is "twenty-one million, five hundred twenty-three thousand, nine hundred fifty-nine".